Portable spar with counter-balance mechanism for bias-mounted head block



May 1, 1962 F. L. LAWRENCE 3,032,322

PORTABLE SPAR WITH COUNTER-BALANCE MECHANISM FOR BIAS-MOUNTED HEAD BLOCKFiled Nov. 17, 1960 2 Sheets-Sheet 1 r w I l! l 2 ,L m /s ,l I .1 2,

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ATTORNEYS May 1, 1962 F. L. LAWRENCE PORTABLE SPAR WITH COUNTER-BALANCEMECHANISM FOR BIAS-MOUNTED HEAD BLOCK 2 Sheets-Sheet 2 Filed Nov. 17,1960 FIG.2

MPUQ ATTORNEYS ire States ada Filed Nov. 17, 1960, Ser. No. 69,882 10Claims. (Cl. 254-190) This invention relates to portable spars of thetype in which the main or haulback sheaves, or both, are located at thehead end of the spar, receiving support from a head block having its hubjournaled for swivel movement about a generally vertical axis.

The spar of the present invention is one in which the swivelled hub ofsaid block is hollow and the main and haulback cables lead downwardlyfrom the respective sheaves through the hollow center of the hub andthence through an opening in the wall of the spar to the spooling drumsof a yarder. The erected spar occupies substantially a verticalposition. The spooling drums are spaced horizontally from the baseof thespar and this perforce dictates for the cables a path angular to thevertical if the cables are to run rub-free between the spooling drumsand the'sheaves. To insure this rub-free path the head blocks swivelaxis is biased from the vertical to bring the hollow center into linewith the wall opening. Since the overhang of the fairleader head blockand its sheave establishes for such head block a weight center which isoffset from the swivel center, the main sheave carried by the head blocknormally tends to gravitate into an established position. This isperforce undesirable when the direction in which the main cable runs outfrom the spar is angular to the direction in which the sheave points byforce of gravity. A conflict arises between the pull force exerted onthe head block by the main cable, to align the head block with thevertical plane in which the cable is working, and the countering forceof gravity. This causes the cable to drag against a flange of thesheave, developing frictional losses and increasing wear on the cable,the sheave, and the journals.

The present invention has for its general object to provide a portablespar of the nature described embodying a mechanism counterbalancingforce of gravity imposed upon a head block swivelled to turn about abiased axis.

This and other more particular objects and advantages will appear and beunderstood in the course of the following description and claims, theinvention consisting in the novel construction and in the adaptation andcombination of parts hereinafter described and claimed.

In the accompanying drawings:

FIGURE 1 is a fragmetary vertical sectional view illustrating the headend of a portable spar engineered to embody the preferred teachings ofthe present invention.

- FIG. 2 is a fragmentary elevational view thereof including anillustration of the main and haulback sheaves which surmount the spar,the scale being reduced from that of FXG. l; and

FIG. 3 is a fragmentary vertical sectional view employing the same scaleas that of FIG. 1 and detailing the thrust-and-journal mounting for theupper end of the head blocks swivelled hub.

Referring to said drawings, the numeral 5 designates the hollow uppersection of a portable spar. Stabilizing guy lines (not shown) run fromstumps or other suitable ground anchors to connectors 6 hung from ananchoring ring 7 which surrounds the spar section and bears upon athrust ring 8 welded or otherwise fixedly secured to the spar section.Below said thrust ring an elongated opening it is provided in said sparsection for the accommodation of main and haulback cables running frompowerdriven spooling drums to respective sheaves 11 and 12. Aself-aligning block 13 which carries the main sheave 11 is mounted atthe head end of the spar for swivel movement about a generally verticalaxis, and a self-aligning block 14 for the haulback sheave 12 is in turnmounted at the head end of the block 13 for swivel movement about acoinciding axis. The swivelled hubs of said blocks are made hollow toaccommodate the cables, and the axis about which the hubs swivel is setat a moderate angle from the center line of the spar in order that thecables will pass, rub-free, through the wall opening ill. Thisangularity is shown as 8. The swivel mounting for the main block 13 isprovided by welding an adapter pipe 15 in the head end of the sparsection and fitting this pipe with a journal bushing 16 at the bottomand a thrustand-journal bushing 17 at the top.

' Such main block projects by its lower end moderately below the adapterpipe. An open annular crown cam 18 is bolted or otherwise rigidlysecured to said projecting lower end with its camming surface facingdownwardly. Said camming surface is regular, being developed with.substantially a'uniform rise in both directions between; high and lowpoints which are at 180 from one another.

' A roller 21, journaled between the fork-arms 22 of a.

yoke for rotation about an axis radial to the cam, rides on the cam andis yieldingly pressed against the latter by a spring 23. The spring usedis an open spiral spring opposing compression, and exerts its thrustloadthrough a ball-joint connection 24 to a vertical slide 25 presenting atits upper end the yoke which supports the roller. A guide 26, forvertical reciprocation of the slide along an axis paralleling the swivelaXis of the block 13, is made an integral part of the spar section.

' Considering low and high as the cam. surface which is remote orproximate, relatively speaking, to the level occupied by a stationarybottoming disk 27 from which the spring 23 takes its purchase, theroller is so located that it rides upon the high point 28 of the camwhen the main sheave 11 hangs in a position dictated by gravity. This isthe position in which the sheave is shown in the drawing. As thevertical plane of the sheave shifts to one sideor the other inconsequence of running the main line on a course angular to saidgravity-dictated plane, the roller responsively works toward the camslow point 29, ultimately occupying the latter when the main line runsout from the spar at 180 to the initial position.

The turning moment exerted upon the cam by the springloaded roller isperforce zero at either of these points in that the roller is occupyinga level surface, so to speak.

- The maximum turning moment which the roller exerts obtains when thecam has moved the slope of the cam then being at its maximum. Thedirectional influence of this turning moment is perforce toward the lowpoint 29 and the design of the cam is such that this moment equals theoppositely directed turning moment due to the ofi-center mounting of themain sheave block.

The load exerted by the spring upon the cam is approximately equal tothe total weight of the main and the haulback sheave assemblies plus anallowance for the weight of the cable carried by each sheave. The cam isdesigned so that, as the main sheave block shifts to any position, thespring-loaded roller 21 exerts upon the cam a turning moment equal tothe turning moment which reflects the degree to which the weight centerof the sheave assembly is laterally removed from a plane radial to theswivel axis of the sheave block into which said weight center normallytends to move by the influence of gravity. This turning moment, toreiterate, varies from zero when the main sheave block occupies eitherthe position in which it is shown or lies diametrically oppositetherefrom, and increases to maximum when moved to a position at rightangles thereto.

It is believed that the invention and the manner of its working willhave been clearly understood from the foregoing detailed description ofmy now-preferred illustrated embodiment. Changes within the spirit ofthe invention will suggest themselves. It is my intention that nolimitations be implied and that the hereto annexed claims be given thebroadest interpretation to which the employed language fairly admits.

What I claim is:

1. In combination with a portable spar having a hollow top sectionprovided with an opening in the wall, a block having a hollow hubjournal-mounted in the head end of said top section above the wallopening for swivel movement about an axis so biased from the verticalcenter of the erected spar that a cable will pass rub-free from thehollow center of the hub through said wall opening to the spooling drumof a yarder occupying a ground position adjacent the base of the spar, aself-aligning sheave over which said cable is fed to said hollow centerof the hub carried by the block and influencing the latter when the sparis approximately vertical to gravitate in one direction by oft-centerdistribution of weight, and means operatively connected with the blockexerting thereon a force counter-balancing said force of gravity.

2. Structure according to claim 1 in which said block is given a journalmounting at its lower end and a thrustand-journal mounting at its upperend.

3. In combination with a portable spar having. a hollow top sectionprovided with an opening in the wall, a block having a hollow hubjournal-mounted in the head end of. said top section above the wallopening for swivel movement about an axis so biased from the verticalcenter of the erected spar that a cable will pass rub-free from thehollow center of the hub through said wall opening to the spooling drumof a yarder occupying a ground position adjacent the base of the spar, aself-aligning sheave over which said cable is fed to said hollow centerof the hub carried by the block and influencing the latter when the sparis approximately vertical to gravitate in one.

direction by ofif-center distribution of weight, a crown cam fixed tosaid block concentric to the swivel axis, the development of said cambeing regular with a single high and low point placed diametricallyopposite to one another, and a spring-loaded roller bearing against saidcam and so placed as to occupy the high point of the cam when the sheaveis pointed in said direction in which it is gravitationally influenced.

4. Structure according to claim 3, said roller being guided forreciprocal motion along an axis paralleling the swivel axis of theblock, the spring load being imposed through a ball-and-socket joint.

5. In a spar, in combination. with a head block carried for swivelmovement by the spar with its, swivel axis so placed as to be biasedfrom the vertical upon erecting the spar to have the same occupy apredetermined position and having mounted upon said block aself-aligning sheave characterized in that its weight distribution insaid erected condition of the spar is off-center in relation to theswivel axis and hence imposes upon the sheave a gravitational forcetending to swing the sheave in one direction, co-acting means carried bythe spar and the block exerting from the spar upon the block a forcecomponent working counter to said force of gravity.

6. In a spar, in combination with a head block carried for swivelmovement by the spar with its swivel axis so placed as to be biased fromthe vertical upon erecting the spar to have the same occupy apredetermined position and having mounted upon said block aself-aligning sheave characterized in that its weight distribution insaid erected condition of the spar is oil-center in relation to theswivel axis and hence imposes upon the sheave a gravitational forcetending to swing the sheave in one direction, co-acting spring-loadedmeans carried by the spar and the block exerting from the spar upon theblock a force component approximately counter-balancing said force ofgravity.

7. In a spar, in combination with a head block carried for swivelmovement by the spar with its swivel axis so placed as to be biased fromthe vertical upon erecting the spar to have the same occupy apredetermined position and having mounted upon said block aself-aligning sheave characterized in that its weight distribution insaid erected condition of the spar is oft-center in relation to theswivel axis and hence imposes upon the sheave a gravitational forcetending to swing the sheave in one direction, co-acting means onecarried by the block and the other by the spar exerting upon the block aturning moment working counter to said force of gravity, one of saidmeans comprising a crown cam fixed to said member by which it is carriedin a position concentric to said swivel axis of the block.

8. A spar according to claim 7, said means which coacts with the camcomprising a roller riding on said cam guided for reciprocal movementin. a direction paralleling the swivel axis of the block, and a springunder compression-loading pressing said roller against the cam.

9. Structure according to claim 7, said cam being a regular camdeveloped so that the counter force exerted is a turning momentapproximately equaling the turning moment due to said oft-centerdistribution of weight.

10. In a spar, in combination with a head block carried for swivelmovement by the spar with its swivel axis so placed as to be biased fromthe vertical upon erecting the spar to have the same occupy apredetermined position and having mounted upon said block aself-aligning sheave characterized in that its Weight distribution insaid erected condition of the spar is off-center in relation to theswivel axis and hence imposes upon the sheave a gravitational forcetending to swing the sheave in one direction, a crown cam fixed to saidblock concentric to the swivel axis, the development of said cam beingregular with a single high and a single low point placed diametricallyopposite one another, and a spring-loaded roller carried by the sparbearing against said cam and so placed as to occupy the high point ofthe cam when the sheave is pointed in said direction in which it isgravitationally influenced.

References Cited in the file of this patent UNITED. STATES PATENTS964,035 Lombard July 12, 1910

